Why The Spin?

[Olvirm]

In the

video before they finish sending the spacecraft off to mars they put it in a spin. Why do they do this?

[astropapi1]

The centrifugal force generates "gravity", but IMO it's not worth it. It's too dangerous and the trip is too short (relatively speaking).

EDIT: Lol, I didn't watch the video and thought he was talking about the Mars One proposal, in which they would tether the hab module to the transfer stage and start a spin.

They used spin-stabilization (as KNova said ), just like bullets that come out a gun. That makes them go straight.

Edited August 6, 2013 by astropapi1

[NovaSilisko]

The centrifugal force generates "gravity", but IMO it's not worth it. It's too dangerous and the trip is too short (relatively speaking).

Er, no... they spin it because spinning things are inherently more stable due to gyroscopic effects and it's a cheap and easy way to provide basic attitude control - http://en.wikipedia.org/wiki/Attitude_control#Spin_stabilization

[Xeldrak]

No, this video is about the Spirit rover. You can stabilize a satellite by letting it spin: Spin-stabilized satellite

Think of a spinning top, as long as it rotates it will stay in the same orientation. This way you can make sure the satellite is pointing in the right direction. For example solar panels towards sun, antenna towards earth.

[Fuzzy Dunlop]

It's the same reason a rifle bullet is spun - to keep it pointing in the same direction. Think of a bike, balancing on it when it's still is difficult, but when the wheels are spinning they try to hold themselves upright.

The upper stage of the Delta 2 rocket is a solid motor with no thrust vectoring. It can't control its direction so instead it is just pointed where it needs to go and then spun up to keep it heading that way. After it's burned out the payload can release weights to slow the spin down, like an ice skater throwing her arms out.

The spirit rover travelled to mars spinning at about 2 revolutions per minute. While the rover was in transit the engineers wanted to keep the comunication antenna pointed at earth and the solar pannels at the sun. They could have used RCS thrusters to keep it steady, but that takes fuel, they could have used reaction wheels, but they are complex and heavy. So the simplest option was just to keep it slowly spinning while pointed the right way.

Edited August 5, 2013 by Fuzzy Dunlop

[Xeldrak]

Actually, spinning it up for the burn, then loosing the angular momentum by extending and then sheding two weight is just an awesomly simple and beautifull solution ^^